Current passenger vehicles have an internal combustion engine which provides output speed and torque over a range of speeds. However, this speed range is not sufficient, nor is the torque range sufficient, to provide good operating characteristics for a vehicle.
To assist the engine in providing adequate operating ranges for the vehicles, a multi-speed power transmission is combined with the engine to form a powertrain for the vehicle. The transmission generally consists of a plurality of gear ratios which may either be manually or hydraulically selected. A vast majority of the current vehicles utilize automatic shifting power transmissions in which an electro-hydraulic control system is utilized to effect the establishment of each individual ratio and to control the interchange between ratios.
The automatic shifting power transmissions generally include two or more planetary gear arrangements which may be coupled in a variety of manner. Generally, with two planetary gearsets being utilized, a four-speed forward planetary gear arrangement or powertrain is provided. Thus, it is obvious that the engine operating range is utilized in each of the four transmission ranges to provide a wide vehicle operating range. The transmission also includes a reverse drive ratio.
Many current vehicles also utilize a five-speed power transmission, however, the current vehicles utilizing five-speed transmissions incorporate interconnected planetary transmissions to provide the five forward speeds and one reverse speed.